To work out 36 × 24, split 24 into 20 and 4. Multiply 36 by 4, then 36 by 20, and add the two answers. 36 × 4 = 144 and 36 × 20 = 720, so 36 × 24 = 864.
An area model shows this as a rectangle cut into four parts: 30 × 20, 30 × 4, 6 × 20 and 6 × 4. Adding the four parts gives the same answer. Long multiplication is a neat way of writing these steps in columns.
Worked example
Work out 47 × 23
- 47 × 3 = 141 and 47 × 20 = 940.
- Add: 141 + 940 = 1 081.
Answer:1 081
Key words
- long multiplication
- multiplying by each digit, then adding
- area model
- a rectangle split into parts to show multiplying
- partial product
- one of the parts you add
Practise this
New questions every time.
Common Core-referenced: 4.NBT.B.5